Implantable medical devices may perform various functions in order to deliver modes of therapy to a patient. For example, cardiac stimulation devices like pacemakers and defibrillators may sense electrical physiologic signals in some modes of therapy in addition to providing electrical pacing signals to one or more chambers of the heart. Some modes of therapy that sense a physiologic signal then use that signal when determining how to control the pacing signal.
Patients that have an implantable medical device may be exposed to magnetic disturbances like those caused by MRI scans or other medical procedures. These magnetic disturbances may result in the device sensing signals that are not actually physiologic but are artificially created by the magnetic disturbances. If the device is allowed to control the pacing signal based on the sensed artificial signal, then the pacing signal may be inappropriate or even harmful for the patient. Therefore, it is commonplace to utilize an exposure mode of therapy during such disturbances. For example, one type of exposure mode deactivates sensing or otherwise ignores the sensed signal and paces asynchronously in a pre-defined pacing configuration with a pre-defined pacing rate. Other types of exposure modes may also be used, such as triggered pacing by filtering externally produced noise from the sensed signal.
Conventionally, the exposure mode of operation is triggered by a clinician using an external device to communicate with the implantable medical device. For example, immediately prior to a patient having an implantable medical device entering an MRI scan, a clinician may program that implantable medical device to enter the exposure mode. Likewise, upon exiting the MRI scan, the clinician then programs the implantable medical device to switch back to a normal mode of operation.
This manual process of entering and exiting the exposure mode of operation presents potential issues. For instance, there is the possibility of human error. Should the fact that the patient has an implantable medical device not be recognized by the personnel responsible for the MRI scan, a clinician may not be present to program the device to enter the exposure mode. Even if the clinician is present, there could be a mistake in programming the device to enter the exposure mode. Furthermore, requiring the clinician to be present to program the device is an added expense to the MM scan procedure.